The early Christian thinker, Tertullian, who wrote at a time of great fragility in the history of the Church, once famously asked: What has Athens to do with Jerusalem? In other words, what does reason have to do with faith?

Nearly two millennia later, our own impulses are often the same: “What does science, scholarship, and worldly wisdom have to do with being a faithful Catholic?” After all, we say, it’s so often in the name of science and ‘progress’ that the faith is forsaken. What could Athens possibly have to do with Jerusalem?

There’s a reason, of course, that we don’t speak of Tertullian much anymore. By the end of his life he had left the Church, which refused to accept his position that natural reason and supernatural faith are opposed. In fact, the Church was headed in quite the opposite direction. Clement of Alexandria expresses beautifully an early understanding of the marriage of faith and reason:

God is the cause of all good things; but of some primarily, as of the Old and the New Testament; and of others by consequence, as philosophy. Perchance, too, philosophy was given to the Greeks directly and primarily, till the Lord should call the Greeks.

Indeed, we can learn a lot from the wisdom of non-Christian thinkers – not the least of which is an appreciation of natural goodness, virtue, and knowledge. It was, after all, the ancient pagans who inspired great saints like Justin Martyr, Augustine and Thomas Aquinas to the heights of their apologiae of the faith. As Socrates said in his own Apology: The unexamined life is not worth living – and this rings true for pagans, atheists, and Christians alike.

But what of the examined life makes it most livable?

Aristotle – perhaps the most virtuous of the pagan thinkers – believed that the use of reason pointed to the best personal actions possible; and that a society grounded in reason was one that pointed to the goodness common to all people. In other words, understanding life makes it worth living precisely because it puts us in closest relation with other people. And when such a society of goodness exists, it echoes the goodness that surpasses it – i.e., the goodness of God.

This Aristotelian teaching holds true today, maybe more than ever. In a culture rent by the politicization of deep moral issues – like abortion, euthanasia, divorce, same-sex marriage, etc. – finding the “good” and the “true,” even as a practicing Catholic, can be a tricky business. At bottom, our culture emphasizes the error of Tertullian, although now from the opposite direction: What can faith possibly have to do with progress? And that turns us off. We’re inclined to retreat from public life, to curl up with our remotes or our missals (depending on which way we break) and relegate faith to Sundays, and to our private lives. In short, we’re led to believe that there’s just no way to bring Christ into the secular world.

But the wisdom of the Church is continuously called to mind. In his controversial Regensburg address, Pope Benedict XVI reminded Christians that “even in the face of such radical skepticism it is still necessary and reasonable to raise the question of God through the use of reason, and to do so in the context of the tradition of the Christian faith.” Similarly, Pope Paul VI – the champion of Humanae vitae – lauds “the courage of the truth, a freedom of spirit in confronting new problems, [and] the intellectual honesty of those who allow Christianity to be contaminated neither by secular philosophy nor by a prejudiced rejection of it.”

At bottom, to be a Christian is to be a public witness and proponent of the truth. It is to engage actively with the culture we live in, to consider its ills and failings – as well as its highpoints – and to resolve them in a spirit of evangelical charity in the service of God and neighbor. This first entails knowing the tenets of our faith; but the other side of the coin is a knowledge and appreciation for the truths – the real truths – of secular progress.

To ascribe to the doctrines of the faith is simply not enough to be holy. Sanctity requires reflection on the meaning of truth, the defense of human dignity, the ordering of life toward a common good, and action in favor of just societies and human flourishing. This is the natural wisdom of the ancient pagans that, time and again, has been shown as the bedrock of interpreting faithfully the teachings of Christ.

This is the examined life; and according to the supernatural wisdom of the Church, it’s the only life worth living.

Andrew Haines is president of the Center for Morality in Public Lifeand a PhD student in Philosophy at The Catholic University of America. He lives in Virginia with his wife, Kathleen, and their son.